Breath of Fresh Air: Feature Articles

Chapter 34: Is Asthma Inherited?

The simple answer to this question is, YES, a tendency to
develop asthma is inherited. If one of your biologic parents has
or had asthma, then you are morely likely to develop asthma than
if he or she did not have asthma. If both of your parents have
asthma, you are even more likely to develop asthma than if only
one parent has this condition.

Another confirmation that asthma is inherited comes from
studies of twins. If one identical twin has asthma, the other
twin (who shares all the same genetic information as his/her
identical twin) is more likely to have asthma than when one of
two non-identical twin siblings (who share some but not all of
their genes in common) has asthma.

However, the whole story is not as simple as the idea that one
either inherits the asthma gene or genes from one's parents
or one does not. For one thing, we know from studies of identical
twins that if one twin has asthma, the chances of the other twin
developing asthma is only 1 in 3, despite the fact that the
inherited information in their genes is identical. For another
thing, we know that some people working in certain occupations
are more likely to develop asthma than if they had not held those
jobs. For instance, if you work in a lumber mill and are exposed
day after day to sawdust from certain types of woods, you may
develop asthma as a result of this exposure. First, workers
experience asthma symptoms only when they breathe in the sawdust,
but with time they develop asthma to all the usual stimuli (such
as exercise, cold air, respiratory tract infections, etc).
Sometimes the asthma goes away if the person stops working in the
sawmill and sometimes it does not.

Like many other diseases, asthma likely results in part from a
tendency, present in one's genes, toward developing the
disease and in part from exposures that one encounters in the
world around us: that is, part heredity, part environment.

We do not know exactly what in our environment contributes to
developing asthma in those with a genetic predisposition. It may
involve breathed particles to which we are allergic, cigarette
smoke or air pollution, viruses or other germs, or some
combination of these and possibly other factors.

Active research, including some being conducted at the Brigham
and Women's Hospital, is attempting to identify the specific
genes responsible for the inherited tendency toward developing
asthma. It is likely that within the next decade we will know at
least some of the genetic pieces to the puzzle of what causes
asthma.